The invention relates to shaving razors having retaining clips that have been drawn from painted sheet metal and to testing the delamination characteristics of painted sheet metal.
Sheet metal that has been painted can thereafter be formed into a desired shape for a product. The application of paint to the metal is often accomplished via a so-called xe2x80x9croll-coatingxe2x80x9d process in which a wave of paint is advanced along a sheet of metal passing through a series of rollers. The roll-coating industry has adopted various tests for measuring delamination resistance of painted sheet metal. These tests include a lead pencil test in which leads of different hardness are used to scratch a painted surface and a T-bend test in which a piece of sheet metal is folded back on itself, and adhesive tape is secured to the paint at the bend to see if the tape can pull the paint off at the bend
Sheet metal has been used to make clips that retain blades on a shaving razor cartridge. Such retaining clips contact the skin and are highly visible to the user. It is therefore important that, if such clips are made from painted material, the formed clips should be free of delaminated areas for performance, comfort and visual esthetics reasons.
In one aspect, the invention features, in general, a shaving razor cartridge including a housing having an upper surface, a housing opening in the upper surface and side surfaces extending downward from the upper surface. Blades are mounted in the opening and supported by the housing, and a retaining clip is secured on the upper surface and has a clip opening around the housing opening. The retaining clip is made of flat painted sheet metal that has been drawn so as to provide an upper surface extending outward of the clip opening and side surfaces extending downward over the side surfaces of the housing. The paint on the sheet metal has sufficient delamination properties to pass a delamination test involving drawing a piece of flat painted sheet metal such that the paint is compressed greater than 35% and inspecting the resulting drawn piece of sheet metal to see if there has been delamination of the paint.
In other aspects, the invention features, in general, a retaining clip for a shaving razor as already described and a drawn product made from a piece of sheet metal that has been painted and thereafter drawn, the paint on the sheet metal having sufficient delamination properties to pass a delamination test as already described.
In another aspect, the invention features, in general, a method of determining whether painted sheet metal has sufficient delamination properties for use in a drawn product. The method involves drawing a piece of the flat painted sheet metal such that paint on the sheet metal is compressed to a predetermined percentage, and inspecting the resulting drawn piece of sheet metal to see there has been delamination.
In another aspect, the invention features, in general, a method of making a drawn product, e.g., a retaining clip for a razor cartridge, from painted sheet metal. The method involves drawing a sample piece of the painted sheet metal such that paint on the sheet metal is compressed to a predetermined percentage, inspecting the resulting drawn piece of sheet metal to see there has been delamination, and, if the inspected piece does not have delamination, drawing pieces of the sheet metal into the form for the drawn product.
Particular embodiments of the invention may include one or more of the following features. The paint on a portion of the clip is subjected to compression between 43% and 45.5%. The drawing of the sample piece involves drawing a circular piece of flat painted sheet metal into a cup shape. The inspecting for delamination involves examination of an edge of the drawn sample piece of sheet metal under magnification. The percentage of compression employed when drawing the sample piece can be determined by carrying out drawing of sample pieces of sheet material a series of times at different percentages of compression, and determining which level of compression most accurately predicts delamination in the drawn product.
Embodiments of the invention may include one or more of the following advantages. The testing of stock painted sheet metal material involves more aggressive drawing than the formation of the actual product, such that there is a high confidence that material passing the testing will not delaminate in manufacture of the formed product. The delamination testing can be adapted and fine-tuned for the particular product being drawn.
Other advantages and features of the invention will be apparent from the following description of a particular embodiment thereof and from the claims.